Fate of polycyclic aromatic hydrocarbons (PAH) in the rhizosphere and mycorrhizosphere of ryegrass

Polycyclic aromatic hydrocarbons (PAH) can be degraded in the rhizosphere b ut may also interact with vegetation by accumulation in plant tissues or ad sorption on root surface. Previous studies have shown that arbuscular mycor rhizal (AM) fungi contribute to the establishment and maintenance of plants in a PAH contaminated soil. We investigated the fate of PAH in the rhizosp here and mycorrhizosphere including biodegradation, uptake and adsorption. Experiments were conducted with ryegrass inoculated or not with Glomus moss eae P2 (BEG 69) and cultivated in pots filled with soil spiked with 5 g kg( -1) of anthracene or with 1 g kg(-1) of a mixture of 8 PAH in a growth cham ber. PAH were extracted from root surfaces, root and shoot tissue and rhizo sphere soil and were analysed by GC-MS. In both experiments, 0.006 - 0.11 p arts per thousand of the initial extractable PAH concentration were adsorbe d to roots, 0.003 - 0.16 parts per thousand were found in root tissue, 0.00 1 parts per thousand in shoot tissue and 36 - 66% were dissipated, suggesti ng that the major part of PAH dissipation in rhizosphere soil was due to bi odegradation or biotransformation. With mycorrhizal plants, anthracene and PAH were less adsorbed to roots and shoot tissue concentrations were lower than with non mycorrhizal plants, which could contribute to explain the ben eficial effect of AM fungi on plant survival in PAH contaminated soils.